Understanding Extinction and Its Causes Revision Notes | GCSE OCR Foundation Biology

What this lesson covers

Students will learn what extinction means and explore the various factors that can lead to species becoming extinct, including environmental changes, hu...

• Define extinction and identify when a species becomes extinct
• Explain the main factors that contribute to species extinction
• Analyse how human activities can lead to species extinction
• Evaluate the impact of environmental changes on species survival

Key ideas to keep in view

Use this lesson to stay inside B5.2 Natural selection and evolution while connecting the detail back to the wider B5: Genes, inheritance and selection topic.

• B5: Genes, inheritance and selection
• B5.2 Natural selection and evolution
• GCSE OCR Foundation Biology

Lesson notes preview

Read the core explanations from Understanding Extinction and Its Causes before testing yourself from memory.

• Imagine if every single dodo bird, every last one, disappeared from Earth forever. That's exactly what happened in 1681 - and it's what we call extinction.
• Extinctions occur when there are no remaining individuals of a species still alive anywhere on Earth.
• This isn't the same as a species being rare or endangered. Extinction means zero individuals left - the species is gone forever. Once extinct, a species cannot come back naturally.
• Think of it like this: if you had the last chocolate bar of a particular type in the world, and you ate it, that chocolate bar type would be 'extinct'. No more can be made because the recipe is lost forever.
• Species don't just disappear randomly. There are specific factors that push them towards extinction. Understanding these causes helps us protect species that are currently at risk.
• The main factors that contribute to extinction fall into several categories. Let's examine each one and see how they work in the real world.
• The process where natural environments are damaged, altered, or completely removed, eliminating the resources species need to survive and reproduce.
• When forests are cut down for farming, or wetlands are drained for building, the animals and plants that lived there lose their homes. No habitat means no food, no shelter, and no place to breed.
• Picture a bird that only nests in old oak trees. If all the oak forests are cleared, where can it nest? Without nesting sites, the bird population crashes and may become extinct.
• Humans have become the biggest driver of extinctions in modern times. Our activities affect species in ways that natural changes rarely do - and much faster than species can adapt.

Continue through the topic

Move to the related lessons or back to the topic page when you need the wider sequence before exam-style practice.